REP SFCG 32-2R1 (Sharing between RNSS & EESS in 1215-1300 ...

antenna beam in azimuth 360 deg each 4.1 seconds with a 14.6 rpm rate. The azimuth beam
footprint is observed at the ground receiver only a maximum of 300 millisec each 4.1 second
period, for a reduction to the PRF by a factor of 0.073 (0.3 sec/ 4.1 sec). As a second example,
Scatterometer1 switches among its three non-overlapping beams every 60 millisec, and then
repeats the switching during the next 180 millisec period, for a reduction to the PRF by a factor
of 0.33 (60 millisec/ 180 millisec).
2.8. Conclusions related to the GPS receiver protection
In conclusion, the overall results of the GPS/EESS (active) study are:
1) The effect of pulsed RF interference from the two spaceborne radars Scatterometer 2 and
SAR3 upon the two RNSS receivers is a change in SNR or C/N 0 of less than 0.1 dB for
Scatterometer 2 and less than -1.4 dB for SAR3 for maximum RFI levels at the RNSS
receivers. With mitigation measures, the SAR3 degradation to SNR can be reduced from
-1.4 dB to -0.1 dB.
2) Accounting for the dynamics and temporal aspects of the radar antenna beam coupling
with the RNSS antenna beam by gating in the test setup reduces the effective duty cycle
that the RFI levels are above the RNSS receiver noise level from the transmit pulse-topulse
duty cycle by a factor of about 40 for Scatterometer 2.
3) Accounting for the overlap of the radar transmit spectrum with the 20 MHz wide RNSS
band reduces the effective pulse-to-pulse duty cycle as well. The Scatterometer 2 signal
with dual 1 MHz wide frequencies is tunable and can be positioned within the 80 MHz
band from 1217.5 MHz to 1297.5 MHz. The 4 MHz wide envelope of the dual spectra
would then overlap the RNSS band when close to the center of the RNSS band at 1227.6
MHz.
4) Accounting for the overlap of the SAR3 transmit spectrum with the 20 MHz wide RNSS
band also reduces its effective pulse-to-pulse duty cycle as well. The SAR3 split
spectrum signal with “20 MHz + 5 MHz” has the lower duty cycle 5 MHz, 5 usec
component located at the lower end of the 1215-1300 band centered around 1220 MHz
such that the higher duty cycle 20 MHz, 20 usec component does not overlap with the
GPS L2 band. The SAR3 20 MHz wide signal can be centered at 1275.5 MHz again with
no overlap with the RNSS band. The SAR3 78 MHz wide signal is centered at 1257.5
MHz with about one-fourth of its bandwidth overlapping the RNSS band.
3-July-2013 Page 16 of 21 REP SFCG 32-2R1